SAN ANTONIO — San Antonio-based Valero Energy Corp. is launching a campaign against proposals to lower carbon emissions by posting signs at its gasoline stations warning customers about the projected high hike in fuel prices if the House-approved bill on carbon cap-and-trade becomes law.

The campaign begins today at all facilities owned by Valero, which has refineries and retail outlets in 40 states.

The U.S. Department of Energy projects that gasoline prices could increase by 77 cents per gallon over the life of the climate-change bill .

Valero, the largest U.S. independent refining company, estimates that its costs for carbon emissions would total $6 billion to $7 billion a year, depending on the auction costs of the permits.

The Waxman-Markey bill, which would force businesses to pay for their carbon emissions, would hit U.S. refining companies especially hard because refiners must account for both emissions from refineries and from the vehicles that burn the fuels, Jim Greenwood, Valero Energy vice president for governmental affairs, said Monday.

The minimum limit for permits is $25 per ton of emissions. Valero refineries emit about 30 million tons per year, but vehicles using Valero fuels emit another 250 million tons of greenhouse, heat-trapping gases.